Process for Producing Blends of Syndiotactic, 1,2-Polybutadiene and Rubbery Elastomers

ABSTRACT

Blends of syndiotactic 1,2-polybutadiene and rubbery elastomers are prepared by a process that comprises polymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within a rubber cement of an elastomeric terpolymer by using a chromium-based, molybdenum-based, or iron-based catalyst composition. Polymer composition comprising the blend with improved properties is also provided.

This application is a continuation of U.S. Ser. No. 10/494,601, which isa continuation-in-part of international application PCT/US02/35402,which claims priority from U.S. Provisional Patent Application No.60/338,840 filed on Nov. 5, 2001, all of which are incorporated hereinby reference.

BACKGROUND

The present invention is directed toward a process for producing blendsof syndiotactic 1,2-polybutadiene and rubbery elastomers. The presentinvention is also directed to a polymer composition comprising a blendof syndiotactic 1,2-polybutadiene and a terpolymer polymerized fromethylene, at least one α-olefin monomer, and at least one diene monomer.

Tire sidewalls protect the ply and are therefore preferably resistant toweathering, ozone, abrasion, and tearing, while providing excellent flexfatigue resistance. Typical tire sidewall formulations include naturalrubber (NR), styrene-butadiene (SBR), butadiene (BR), and halogenatedbutyl (HIIR). Ethylene-propylene-diene terpolymer (EPDM) is attractivebecause of its resistance to weathering and ozone.

EPDM, however, is not compatible with butadiene rubber and fillers, andhas poor cut growth resistance. Blends of EPDM with crystalline polymershave shown improved cut growth properties at room temperature. Atelevated temperatures, however, these materials have poor cut growthproperties.

Syndiotactic 1,2-polybutadiene (sPB) is a crystalline thermoplasticresin that has a stereoregular structure in which the side-chain vinylgroups are located alternately on the opposite sides in relation to thepolymeric main chain. sPB uniquely exhibits the properties of bothplastics and rubber, and therefore it has many uses. It can also beblended into and co cured with natural and synthetic rubbers.

Syndiotactic 1,2-polybutadiene can be made by solution, emulsion, orsuspension polymerization. Generally, syndiotactic 1,2-polybutadiene hasa melting temperature within the range of about 195° C. to about 215°C., but due to processability considerations, it is generally desirablefor syndiotactic 1,2 polybutadiene to have a melting temperature of lessthan about 195° C.

Because syndiotactic 1,2-polybutadiene is insoluble in common solventsat normal polymerization temperatures, a common technical difficulty inthe synthesis of syndiotactic 1,2-polybutadiene is that thepolymerization mixture is an extremely thick slurry at the commerciallydesirable polymer concentration of 10% to 25% by weight. This thickslurry becomes difficult to stir and transfer, thereby diminishing heattransfer efficiency and interfering with proper process control. Also,the slurry contributes to reactor fouling due to the undesirablebuild-up of insoluble polymer on the baffles, agitator blades, agitatorshafts, and walls of the polymerization reactor. It is thereforenecessary to clean the reactor on a regular basis, which results infrequent shutdowns of continuous processes and serious limitations ofthe run length of batch processes. The task of cleaning the fouledreactor is generally difficult and time-consuming. All of thesedrawbacks detrimentally affect productivity and the cost of operation.

The physical properties of rubbery elastomers can be improved byblending crystalline polymers therein. For example, incorporatingsyndiotactic 1,2-polybutadiene into rubber compositions that areutilized in the supporting carcass of tires greatly improves the greenstrength of those compositions. Also, incorporating syndiotactic1,2-polybutadiene into tire tread compositions can reduce heat build-upand improve wear characteristics of tires. The green strength ofsynthetic rubbers such as cis-1,4-polybutadiene can also be improved byincorporating a small amount of syndiotactic 1,2-polybutadiene.

Blends of crystalline polymers and rubbery elastomers are typicallyprepared by standard mixing techniques. For example, these blends can beprepared by mixing or kneading and heat-treating a crystalline polymerand a rubbery elastomer by utilizing generally known mixing equipmentsuch as a Banbury mixer, a Brabender mixer, an extruder, a kneader, or amill mixer. These high-temperature mixing procedures, however, havecertain drawbacks including high processing costs, polymer degradationand crosslinking, inadequate mixing, as well as various processlimitations. Due to the high vinyl content of syndiotactic1,2-polybutadiene, polymer degradation and crosslinking is aparticularly severe problem for mixing syndiotactic 1,2-polybutadienewith elastomers at high temperatures.

Attempts to polymerize 1,3-butadiene into syndiotactic 1,2-polybutadienewithin a rubber cement have been hampered by catalyst inefficiencies andtoxicities. For example, U.S. Pat. No. 4,379,889 teaches polymerizing1,3-butadiene into syndiotactic 1,2-polybutadiene within a rubber cementby using a catalyst system comprising a cobalt compound, adialkylaluminum halide, carbon disulfide, and an electron donativecompound. And, U.S. Pat. No. 5,283,294 teaches a similar process thatemploys a catalyst system comprising a cobalt compound, anorganoaluminum compound, and carbon disulfide. These methods, however,are inferior because the catalyst systems that are employed suffer fromlow catalytic activity, poor stereoselectivity, the need for toxic,halogenated solvents, and the many drawbacks associated with carbondisulfide including low flash point, obnoxious smell, high volatilityand toxicity.

Therefore, it would be advantageous to develop a new and significantlyimproved process for producing blends of syndiotactic 1,2-polybutadieneand rubbery elastomers.

SUMMARY OF THE INVENTION

In general, the present invention provides a process for preparingblends of syndiotactic 1,2-polybutadiene and rubbery elastomerscomprising the steps of (1) providing a mixture of a rubber cement and1,3-butadiene monomer; and (2) polymerizing the 1,3-butadiene intosyndiotactic 1,2-polybutadiene within the rubber cement by using acatalyst composition that is formed by combining, (a) achromium-containing compound, (b) a hydrogen phosphite, and (c) anorganomagnesium compound or (a) a molybdenum-containing compound or aniron-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound.

The present invention further provides a process for preparing blends ofsyndiotactic 1,2-polybutadiene and rubbery elastomers comprising thesteps of (1) providing a mixture of a rubber cement and 1,3-butadienemonomer, where the rubber cement comprises an elastomeric terpolymerpolymerized from ethylene, at least one -olefin monomer, and at leastone diene monomer; and (2) preparing a catalyst composition, where thecatalyst composition is prepared by combining, outside the presence ofthe mixture of rubber cement and monomer, (a) a chromium-containingcompound, (b) a hydrogen phosphite, and (c) an organomagnesium compoundor (a) a molybdenum-containing compound or an iron-containing compound,(b) a hydrogen phosphite, and (c) an organoaluminum compound; and (3)adding the catalyst composition to the mixture and thereby polymerizingthe 1,3-butadiene monomer into syndiotactic l 1,2-polybutadiene withinthe rubber cement.

Advantageously, the process of this invention directly provides blendsof syndiotactic 1,2-polybutadiene and rubbery elastomers by synthesizingsyndiotactic 1,2-polybutadiene within a rubber cement and therebyobviates the need for high-temperature mixing. Also, good dispersion ofsyndiotactic 1,2-polybutadiene throughout rubbery elastomers can beeasily and economically achieved. Significantly, the process of thisinvention eliminates the problems of high processing costs, polymerdegradation and crosslinking, inadequate mixing, and various processlimitations that are associated with high-temperature mixing procedures.The process of this invention also alleviates the problems of polymercement thickness and reactor fouling that are associated with thesynthesis of syndiotactic 1,2-polybutadiene in the absence of a rubberyelastomer.

In addition, the catalyst systems employed in this invention have veryhigh catalytic activity and stereoselectivity for the syndiospecificpolymerization of 1,3-butadiene. This activity and selectivity, amongother advantages, allows syndiotactic 1,2-polybutadiene to be producedin very high yields within a rubber cement. Additionally, these catalystcompositions do not contain carbon disulfide, and therefore thetoxicity, objectionable smell, dangers, and expense associated with theuse of carbon disulfide are eliminated. Further, the chromium,molybdenum, and iron compounds are generally stable, inexpensive,relatively innocuous, and readily available. Furthermore, these catalystcompositions have high catalytic activity in a wide variety of solventsincluding the environmentally preferred nonhalogenated solvents such asaliphatic and cycloaliphatic hydrocarbons.

Furthermore, blends of syndiotactic 1,2-polybutadiene and elastomericterpolymers polymerized from ethylene, at least one α-olefin monomer,and at least one diene monomer, prepared by the process of the presentinvention, exhibit improved cut growth resistance at elevatedtemperatures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is generally directed toward a process forproducing blends of syndiotactic 1,2-polybutadiene and rubberyelastomers. Blends of syndiotactic 1,2-polybutadiene and rubberyelastomers can be directly produced by polymerizing 1,3-butadienemonomer into syndiotactic 1,2 polybutadiene within a rubber cement byusing chromium-based, molybdenum-based, or iron-based catalystcompositions.

The process includes the steps of: (1) providing a mixture of a rubbercement and 1,3-butadiene monomer, where the rubber cement includes atleast one rubbery elastomer within an organic solvent, and (2)polymerizing the 1,3 butadiene monomer into syndiotactic1,2-polybutadiene within the rubber cement by using a chromium-based,molybdenum-based, or iron-based catalyst composition. The chromium-basedcatalyst composition is formed by combining (a) a chromium-containingcompound, (b) a hydrogen phosphite, and (c) an organomagnesium compound.The molybdenum-based catalyst composition is formed by combining (a) amolybdenum-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound. The iron-based catalyst composition is formedby combining (a) an iron-containing compound, (b) a hydrogen phosphite,and (c) an organoaluminum compound.

The rubber cement employed in this invention is a solution, preferablyviscous, of at least one rubbery elastomer in an organic solvent.Virtually any type of rubbery elastomer can be used to prepare therubber cement. In a preferred embodiment, the rubbery elastomer includesan elastomeric terpolymer polymerized from ethylene, at least oneα-olefin monomer, and at least one diene monomer. The α-olefins mayinclude, but are not limited to, propylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-octene, 1-decene, or combinations thereof. Thediene monomers may include, but are not limited to,5-ethylidene-2-norbornene, 1,4-hexadiene, 5-methylene-2-norbornene,1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene,1,3-cyclopentadiene, 1,4-cyclohexadiene, dicyclopentadiene,5-vinyl-2-norbornene and the like, or a combination thereof. When theterpolymer is polymerized from ethylene, propylene, and at least onediene monomer, the polymer may be referred to as EPDM.

Elastomeric terpolymers prepared from ethylene, at least one α-olefinmonomer, and at least one diene monomer may be prepared by methods knownin the art, and they are commercially available under the tradenamesVistalon™ (Exxon Mobil Chemical Co.; Houston, Tex.), Keltan™ (DSMCopolymers; Baton Rouge, La.), Nordel™ IP (DuPont Dow Elastomers;Wilmington, Del.), ElastoFlo™ (Union Carbide; Danbury, Conn.), and Buna™(Bayer Corp.; Germany).

The elastomeric terpolymers described above may be used in combinationwith each other, or other rubbery elastomers. Examples of other rubberyelastomers include, but are not limited to, natural rubber, low-vinylpolybutadiene, cis-1,4-polybutadiene, amorphous 1,2-polybutadiene,low-vinyl polyisoprene, cis-1,4-polyisoprene, polyisobutylene, neoprene,ethylene-propylene copolymer rubber (EPR), styrene-butadiene rubber(SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber(SIBR), styrene-butadiene-styrene block copolymer (SBS),styrene-butadiene block copolymer (SB), hydrogenated styrenebutadiene-styrene block copolymer (SEBS), hydrogenated styrene-butadieneblock copolymer (SEB), styrene-isoprene-styrene block copolymer (SIS),styrene-isoprene block copolymer (SI), hydrogenatedstyrene-isoprene-styrene block copolymer (SEPS), hydrogenatedstyrene-isoprene block copolymer (SEP), polysulfide rubber, acrylicrubber, urethane rubber, silicone rubber, epichlorohydrin rubber, andthe like. Mixtures of the above rubbery elastomers may also be used.These rubbery elastomers are well known and, for the most part, arecommercially available. Also, those skilled in the art will be able toreadily synthesize these rubbery elastomers by using techniques that arewell known in the art.

The rubber cement can be prepared by dissolving the rubbery elastomersin an organic solvent. When commercially available rubbery elastomersare employed to prepare the rubber cement, it may be necessary to purifythe commercial products before use in order to remove residual water andadditives that may become catalyst poisons in the subsequent step ofpolymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadienewithin the rubber cement.

In one embodiment, the rubber cement is prepared in situ by polymerizingone or more appropriate monomers into rubbery elastomers in an organicsolvent within the same reactor that is subsequently used forpolymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene. Manymethods of synthesizing rubbery elastomers are known in the art.Preferably, however, the catalyst utilized in preparing the rubberyelastomers should not contain any ingredients that may interfere withthe catalyst subsequently used in the step of polymerizing 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene within the rubber cement.

In preparing the rubber cement, it is desirable to select an organicsolvent that is inert with respect to the catalyst systems that will beemployed to synthesize the rubbery elastomers and the syndiotactic1,2-polybutadiene. Suitable types of organic solvents that can beutilized in preparing the rubber cement include, but are not limited to,aliphatic, cycloaliphatic, and aromatic hydrocarbons. Somerepresentative examples of suitable aliphatic solvents includen-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane,isopentane, isohexanes, isoheptanes, isooctanes, 2,2-dimethylbutane,petroleum ether, kerosene, petroleum spirits, and the like. Somerepresentative examples of suitable cycloaliphatic solvents includecyclopentane, cyelohexane, methylcyclopentane, methylcyclohexane, andthe like. Some representative examples of suitable aromatic solventsinclude benzene, toluene, xylenes, ethylbenzene, diethylbenzene,mesitylene, and the like. Commercial mixtures of the above hydrocarbonsmay also be used. For environmental reasons, aliphatic andcycloaliphatic solvents are highly preferred.

The concentration of the rubbery elastomers in the rubber cement variesdepending on the types of the rubbery elastomers and organic solventemployed. The concentration of the rubbery elastomers within the cementis preferably from about 5% to about 35% by weight of the rubber cement,more preferably from about 10% to 30% by weight of the rubber cement,and even more preferably from about 15% to about 25% by weight of therubber cement.

The rubber cement is then utilized as a polymerization medium for thestereospecific polymerization of 1,3-butadiene monomer into syndiotactic1,2-polybutadiene. Thus, 1,3-butadiene monomer, catalyst composition,and optionally additional organic solvent are added to the rubbercement. The order in which the 1,3-butadiene monomer, the catalystcomposition, and the solvent are added to the rubber cement does notlimit the scope of the invention, although it may be preferable to addthe catalyst composition, or at least an ingredient thereof, prior toadding the 1,3-butadiene monomer.

The amount of 1,3-butadiene monomer added to the rubber cement iscontingent upon the proportion of syndiotactic 1,2-polybutadiene desiredin the resultant polymer blend. The additional organic solvent can beselected from the group of the organic solvents mentioned above for thepreparation of the rubber cement, and may be the same as or differentfrom the organic solvent used in preparing the rubber cement. Theaddition of 1,3-butadiene monomer to the rubber cement may not berequired in the case where 1,3-butadiene monomer is employed to preparethe rubbery elastomers and the polymerization is stopped before all the1,3-butadiene is consumed, thereby providing the remaining 1,3-butadienemonomer for synthesizing the syndiotactic 1,2-polybutadiene without theneed to add additional 1,3-butadiene monomer.

Although the preferred embodiment of the present invention is directedtoward the polymerization of 1,3-butadiene into syndiotactic1,2-polybutadiene within a rubber cement, other conjugated dienemonomers can be polymerized to form conjugated diene polymers,preferably crystalline polymers, within a rubber cement.

Chromium-based catalyst compositions useful for the polymerization of1,3-butadiene into syndiotactic 1,2-polybutadiene are described in U.S.Pat. Nos. 6,201,080 and 6,117,956, which are incorporated herein byreference. The preferred chromium-based catalyst composition is formedby combining (a) a chromium-containing compound, (b) a hydrogenphosphite, and (c) an organomagnesium compound. In addition to the threecatalyst ingredients (a), (b), and (c), other organometallic compoundsor Lewis bases that are known in the art can also be added, if desired.

Various chromium-containing compounds or mixtures thereof can beemployed as ingredient (a) of the chromium-based catalyst compositionutilized in this invention. It is generally advantageous to employchromium-containing compounds that are soluble in a hydrocarbon solventsuch as aromatic hydrocarbons, aliphatic hydrocarbons, or cycloaliphatichydrocarbons. Hydrocarbon-insoluble chromium-containing compounds,however, can be suspended in the polymerization medium to form thecatalytically active species and are therefore also useful.

The chromium atom in the chromium-containing compounds can be in variousoxidation states ranging from 0 up to +6. Divalent chromium compounds(also called chromous compounds), wherein the chromium is in the +2oxidation state, and trivalent chromium compounds (also called chromiccompounds), wherein the chromium is in the +3 oxidation state arepreferred. Suitable types of chromium-containing compounds that can beutilized include, but are not limited to, chromium carboxylates,chromium organophosphates, chromium organophosphonates, chromiumorganophosphinates, chromium carbamates, chromium dithiocarbamates,chromium xanthates, chromium 13-diketonates, chromium alkoxides oraryloxides, chromium halides, chromium pseudo-halides, chromiumoxyhalides, and organochromium compounds.

Suitable chromium carboxylates include chromium formate, chromiumacetate, chromium acrylate, chromium methacrylate, chromium valerate,chromium gluconate, chromium citrate, chromium fumarate, chromiumlactate, chromium maleate, chromium oxalate, chromium 2-ethylhexanoate,chromium neodecanoate, chromium naphthenate, chromium stearate, chromiumoleate, chromium benzoate, and chromium picolinate.

Suitable chromium organophosphates include chromium dibutyl phosphate,chromium dipentyl phosphate, chromium dihexyl phosphate, chromiumdiheptyl phosphate, chromium dioctyl phosphate, chromiumbis(1-methylheptyl) phosphate, chromium bis(2-ethylhexyl)phosphate,chromium didecyl phosphate, chromium didodecyl phosphate, chromiumdioctadecyl phosphate, chromium dioleyl phosphate, chromium diphenylphosphate, chromium bis(p-nonylphenyl)phosphate, chromiumbutyl(2-ethylhexyl)phosphate, chromium(1-methylheptyl)(2-ethylhexyl)phosphate, and chromium (2-ethylhexyl)(p-nonylphenyl)phosphate.

Suitable chromium organophosphonates include chromium butyl phosphonate,chromium pentyl phosphonate, chromium hexyl phosphonate, chromium heptylphosphonate, chromium octyl phosphonate, chromium(1methylheptyl)phosphonate, chromium (2-ethylhexyl)phosphonate, chromiumdecyl phosphonate, chromium dodecyl phosphonate, chromium octadecylphosphonate, chromium oleyl phosphonate, chromium phenyl phosphonate,chromium(p-nonylphenyl)phosphonate, chromium butyl butylphosphonate, 10chromium pentyl pentylphosphonate, chromium hexyl hexylphosphonate,chromium heptyl heptylphosphonate, chromium octyl octylphosphonate,chromium (1-methylheptyl) (1-methylheptyl)phosphonate, chromium(2-ethylhexyl)(2-ethylhexyl)phosphonate, chromium decyldecylphosphonate, chromium dodecyl dodecylphosphonate, chromiumoctadecyl octadecylphosphonate, chromium oleyl oleylphosphonate,chromium phenyl phenylphosphonate, chromium(p-nonylphenyl)(p-nonylphenyl)phosphonate, chromium butyl(2-ethylhexyl)phosphonate, chromium (2-ethylhexyl)butylphosphonate,chromium (1-methylheptyl)(2-ethylhexyl)phosphonate, chromium(2-ethylhexyl)(1-methylheptyl)phosphonate, chromium(2-ethylhexyl)(p-nonylphenyl)phosphonate, and chromium(p-nonylphenyl)(2-ethylhexyl) phosphonate.

Suitable chromium organophosphinates include chromium butylphosphinate,chromium pentylphosphinate, chromium hexylphosphinate, chromiumheptylphosphinate, chromium octylphosphinate, chromium(1-methylheptyl)phosphinate, chromium (2-ethylhexyl)phosphinate,chromium decylphosphinate, chromium dodecylphosphinate, chromiumoctadecylphosphinate, chromium oleylphosphinate, chromiumphenylphosphinate, chromium(p-nonylphenyl)phosphinate, chromiumdibutylphosphinate, chromium dipentylphosphinate, chromiumdihexylphosphinate, chromium diheptylphosphinate, chromiumdioctylphosphinate, chromium bis(1-methylheptyl)phosphinate, chromiumbis(2-ethylhexyl)phosphinate, chromium didecylphosphinate, chromiumdidodecylphosphinate, chromium dioctadecylphosphinate, chromiumdioleylphosphinate, chromium diphenylphosphinate, chromiumbis(p-nonylphenyl)phosphinate, chromium butyl(2-ethylhexyl)phosphinate,chromium (1-methylheptyl)(2-ethylhexyl)phosphinate, and chromium(2-ethylhexyl)(p-nonylphenyl)phosphinate.

Suitable chromium carbamates include chromium dimethylcarbamate,chromium diethylcarbamate, chromium diisopropylcarbamate, chromiumdibutylcarbamate, and chromium dibenzylcarbamate.

Suitable chromium dithiocarbamates include chromiumdimethyldithiocarbamate, chromium diethyldithiocarbamate, chromiumdiisopropyldithiocarbamate, chromium dibutyldithiocarbamate, andchromium dibenzyldithiocarbamate.

Suitable chromium xanthates include chromium methylxanthate, chromiumethylxanthate, chromium isopropylxanthate, chromium butylxanthate, andchromium benzylxanthate.

Suitable chromium diketonates include chromium acetylacetonate, chromiumtrifluoroacetylacetonate, chromium hexafluoroacetylacetonate, chromiumbenzoylacetonate, chromium 2,2,6,6-tetramethyl-3,5-heptanedionate,chromium dioxide bis(acetylacetonate), chromium dioxidebis(trifluoroacetylacetonate), chromium dioxidebis(hexafluoroacetylacetonate), chromium dioxide bis(benzoylacetonate),and chromium dioxide bis(2,2,6,6-tetramethyl-3,5-heptanedionate).

Suitable chromium alkoxides or aryloxides include chromium methoxide,chromium ethoxide, chromium isopropoxide, chromium 2-ethylhexoxide,chromium phenoxide, chromium nonylphenoxide, and chromium naphthoxide.

Suitable chromium halides include chromium hexafluoride, chromiumpentafluoride, chromium tetrafluoride, chromium trifluoride, chromiumpentachloride, chromium tetrachloride, chromium bichloride, chromiumtetrabromide, chromium tribromide, chromium triiodide, and chromiumdiiodide.

Suitable chromium pseudo-halides include chromium cyanide, chromiumcyanate, chromium thiocyanate, and chromium azide.

Suitable chromium oxyhalides include chromium oxytetrafluoride, chromiumdioxydifluoride, chromium oxytetrachloride, chromium oxytrichloride,chromium dioxydichloride, chromium oxytribromide, and chromiumdioxydibromide.

The term “organochromium compound” refers to any chromium compoundcontaining at least one chromium-carbon bond. Suitable organochromiumcompounds include tris(allyl)chromium, tris(methallyl)chromium,tris(crotyl) chromium, bis(cyclopentadienyl)chromium (also calledchromocene), bis(pentamethylcyclopentadienyl)chromium,bis(ethylbenzene)chromium (also called decamethylchromocene),bis(benzene)chromium, bis(ethylbenzene)chromium,bis(mesitylene)chromium, bis(pentadienyl)chromium,bis(2,4-dimethylpentadienyl) chromium, bis(allyl)tricarbonylchromium,(cyclopentadienyl)(pentadienyl)chromium, terra(1-norbornyl)chromium,(trimethylenemethane)tetracarbonylchromium,bis(butadiene)dicarbonylchromium, (butadiene)tetracarbonylchromium, andbis(cyclooctatetraene)chromium.

Useful hydrogen phosphite compounds that can be employed as ingredient(b) of the chromium-based catalyst composition utilized in thisinvention are either acyclic hydrogen phosphites, cyclic hydrogenphosphites, or mixtures thereof.

In general, acyclic hydrogen phosphites may be represented by thefollowing keto-enol tautomeric structures:

where R₁ and R₂, which may be the same or different, are mono-valentorganic groups. Preferably, R₁ and R₂ are hydrocarbyl groups such as,but not limited to, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,cycloalkenyl, substituted cycloalkenyl, aryl, allyl, substituted aryl,aralkyl, alkaryl, and alkynyl groups, with each group preferablycontaining from 1 carbon atom, or the appropriate minimum number ofcarbon atoms to form the group, up to 20 carbon atoms. These hydrocarbylgroups may contain heteroatoms such as, but not limited to, nitrogen,oxygen, silicon, sulfur, and phosphorus atoms. The acyclic hydrogenphosphites exist mainly as the keto tautomer (shown on the left), withthe enol tautomer (shown on the right) being the minor species. Theequilibrium constant for the above-mentioned tautomeric equilibrium isdependent upon factors such as the temperature, the types of R₁ and R₂groups, the type of solvent, and the like. Both tautomers may beassociated in dimeric, trimeric or oligomeric forms by hydrogen bonding.Either of the two tautomers or mixtures thereof can be employed as theingredient (b) of the chromium-based catalyst composition utilized inthis invention.

Suitable acyclic hydrogen phosphites include dimethyl hydrogenphosphite, diethyl hydrogen phosphite, dibutyl hydrogen phosphite,dihexyl hydrogen phosphite, dioctyl hydrogen phosphite, didecyl hydrogenphosphite, didodecyl hydrogen phosphite, dioctadecyl hydrogen phosphite,bis(2,2,2 trifluoroethyl)hydrogen phosphite, diisopropyl hydrogenphosphite, bis(3,3 dimethyl-2-butyl)hydrogen phosphite,bis(2,4-dimethyl-3-pentyl)hydrogen phosphite, di-t-butyl hydrogenphosphite, bis(2-ethylhexyl)hydrogen phosphite, dineopentyl hydrogenphosphite, bis(cyclopropylmethyl)hydrogen phosphite,bis(cyclobutylmethyl) hydrogen phosphite, bis(cyclopentylmethyl)hydrogenphosphite, bis(cyclohexylmethyl)hydrogen phosphite, dicyclobutylhydrogen phosphite, dicyclopentyl hydrogen phosphite, dicyclohexylhydrogen phosphite, dimethyl hydrogen phosphite, diphenyl hydrogenphosphite, dinaphthyl hydrogen phosphite, dibenzyl hydrogen phosphite,bis(1-naphthylmethyl)hydrogen phosphite, diallyl hydrogen phosphite,dimethallyl hydrogen phosphite, dicrotyl hydrogen phosphite, ethyl butylhydrogen phosphite, methyl hexyl hydrogen phosphite, methyl neopentylhydrogen phosphite, methyl phenyl hydrogen phosphite, methyl cyclohexylhydrogen phosphite, methyl benzyl hydrogen phosphite, and the like.Mixtures of the above dihydrocarbyl hydrogen phosphites may also beutilized.

In general, cyclic hydrogen phosphites contain a divalent organic groupthat bridges between the two oxygen atoms that are singly-bonded to thephosphorus atoms. These cyclic hydrogen phosphites may be represented bythe following keto-enol tautomeric structures:

where R₃ is a divalent organic group. Preferably, R₃ is a hydrocarbylenegroup such as, but not limited to, alkylene, cycloalkylene, substitutedalkylene, substituted cycloalkylene, alkenylene, cycloalkenylene,substituted alkenylene, substituted cycloalkenylene, arylene, andsubstituted arylene groups, with each group preferably containing from 1carbon atom, or the appropriate minimum number of carbon atoms to formthe group, up to 20 carbon atoms. These hydrocarbylene groups maycontain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. The cyclic hydrogen phosphitesexist mainly as the keto tautomer (shown on the left), with the enoltautomer (shown on the right) being the minor species. The equilibriumconstant for the above-mentioned tautomeric equilibrium is dependentupon factors such as the temperature, the types of R₃ group, the type ofsolvent, and the like. Both tautomers may be associated in dimeric,trimeric or oligomeric forms by hydrogen bonding. Either of the twotautomers or mixtures thereof can be employed as the ingredient (b) ofthe chromium-based catalyst composition utilized in this invention.

The cyclic hydrogen phosphites may be synthesized by thetransesterification reaction of an acyclic dihydrocarbyl hydrogenphosphite (usually dimethyl hydrogen phosphite or diethyl hydrogenphosphite) with an alkylene diol or an arylene diol. Procedures for thistransesterification reaction are well known to those skilled in the art.Typically, the transesterification reaction is carried out by heating amixture of an acyclic dihydrocarbyl hydrogen phosphite and an alkylenediol or an arylene diol. Subsequent distillation of the side-productalcohol (usually methanol or ethanol) that results from thetransesterification reaction leaves the new-made cyclic hydrogenphosphite.

Suitable cyclic alkylene hydrogen phosphites include2-oxo-(2H)-5-butyl-5-ethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5,5-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-1,3,2-dioxaphosphorinane, 2-oxo-(2H)-4-methyl1,3,2-dioxaphosphorinane,2-oxo-(2H)-5-ethyl-5-methyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5,5-diethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5-methyl-5-propyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-isopropyl-5,5-di methyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4,6-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-propyl-5-ethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-methyl-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-dimethyl-1,3,2-dioxaphospholane,2-oxo-(2H)-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, and the like.Mixtures of the above cyclic alkylene hydrogen phosphites may also beutilized.

Suitable cyclic arylene hydrogen phosphites include2-oxo-(2H)-4,5-benzo-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(3′-methylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(4′-methylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(4′-tert-butylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-naphthalo-1,3,2-dioxaphospholane, and the like. Mixturesof the above cyclic arylene hydrogen phosphites may also be utilized.

The chromium-based catalyst composition utilized in this inventionfurther comprises an organomagnesium compound, which has been designatedas ingredient (c). As used herein, the term “organomagnesium compound”refers to any magnesium compound containing at least onemagnesium-carbon bond. Organomagnesium compounds that are soluble in ahydrocarbon solvent are preferably employed.

A preferred class of organomagnesium compounds that can be utilized asingredient (c) of the chromium-based catalyst composition utilized inthis invention is represented by the general formula Mg(R₄)₂, where eachR₄, which may be the same or different, is a mono-valent organic group,with the proviso that the group is attached to the magnesium atom via acarbon atom. Preferably, each R₄ is a hydrocarbyl group such as, but notlimited to, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,cycloalkenyl, substituted cycloalkenyl, aryl, allyl, substituted aryl,aralkyl, alkaryl, and alkynyl groups, with each group preferablycontaining from 1 carbon atom, or the appropriate minimum number ofcarbon atoms to form the group, up to about 20 carbon atoms. Thesehydrocarbyl groups may contain heteroatoms such as, but not limited to,nitrogen, oxygen, silicon, sulfur, and phosphorus atom.

Suitable dihydrocarbylmagnesium compounds include diethylmagnesium,di-n-propylmagnesium, diisopropylmagnesium, dibutylmagnesium,dihexylmagnesium, diphenylmagnesium, dibenzylmagnesium, and mixturesthereof. Dibutylmagnesium is particularly useful due to its availabilityand its solubility in aliphatic and cycloaliphatic hydrocarbon solvents.

Another class of organomagnesium compounds that can be utilized asingredient (c) of the catalyst composition utilized in this invention isrepresented by the general formula R₅MgX, where R₅ is a mono-valentorganic group, with the proviso that the group is attached to themagnesium atom via a carbon atom, and X is a hydrogen atom, a halogenatom, a carboxylate group, an alkoxide group, or an aryloxide group.Preferably, R₅ is a hydrocarbyl group such as, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atom, or the appropriate minimum number of carbon atoms to formthe group, up to about 20 carbon atoms. These hydrocarbyl groups maycontain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. Preferably, X is a carboxylategroup, an alkoxide group, or an aryloxide group, with each grouppreferably containing 1 to 20 carbon atoms.

Suitable types of organomagnesium compounds that are represented by thegeneral formula R₅MgX include, but are not limited to,hydrocarbylmagnesium hydride, hydrocarbylmagnesium halide,hydrocarbylmagnesium carboxylate, hydrocarbylmagnesium alkoxide,hydrocarbylmagnesium aryloxide, and mixtures thereof.

Suitable organomagnesium compounds that are represented by the generalformula R₅MgX include methylmagnesium hydride, ethylmagnesium hydride,butylmagnesium hydride, hexylmagnesium hydride, phenylmagnesium hydride,benzylmagnesium hydride, methylmagnesium chloride, ethylmagnesiumchloride, butylmagnesium chloride, hexylmagnesium chloride,phenylmagnesium chloride, benzylmagnesium chloride, methylmagnesiumbromide, ethylmagnesium bromide, butylmagnesium bromide, hexylmagnesiumbromide, phenylmagnesium bromide, benzylmagnesium bromide,methylmagnesium hexanoate, ethylmagnesium hexanoate, butylmagnesiumhexanoate, hexylmagnesium hexanoate, phenylmagnesium hexanoate,benzylmagnesium hexanoate, methylmagnesium ethoxide, ethylmagnesiumethoxide, butylmagnesium ethoxide, hexylmagnesium ethoxide,phenylmagnesium ethoxide, benzylmagnesium ethoxide, methylmagnesiumphenoxide, ethylmagnesium phenoxide, butylmagnesium phenoxide,hexylmagnesium phenoxide, phenylmagnesium phenoxide, benzylmagnesiumphenoxide, and the like, and mixtures thereof.

Molybdenum-based catalyst compositions are described in U.S. Ser. No.09/700,017, which is incorporated herein by reference. Themolybdenum-based catalyst composition is formed by combining (a) amolybdenum-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound. In addition to the three catalyst ingredients(a), (b), and (c), other organometallic compounds or Lewis bases canalso be added, if desired.

Various molybdenum-containing compounds or mixtures thereof can beemployed as ingredient (a) of the catalyst composition utilized in thisinvention. It is generally advantageous to employ molybdenum-containingcompounds that are soluble in hydrocarbon solvents such as aromatichydrocarbons, aliphatic hydrocarbons, or cycloaliphatic hydrocarbons.Hydrocarbon insoluble molybdenum-containing compounds, however, can besuspended in the polymerization medium to form the catalytically activespecies and are therefore also useful.

The molybdenum atom in the molybdenum-containing compounds can be invarious oxidation states ranging from 0 up to +6. Suitable types ofmolybdenum-containing compounds that can be utilized include, but arenot limited to, molybdenum carboxylates, molybdenum organophosphates,molybdenum organophosphonates, molybdenum organophosphinates, molybdenumcarbamates, molybdenum dithiocarbamates, molybdenum xanthates,molybdenum 13-diketonates, molybdenum alkoxides or aryloxides,molybdenum halides, molybdenum pseudo-halides, molybdenum oxyhalides,and organomolybdenum compounds.

Suitable molybdenum carboxylates include molybdenum formate, molybdenumacetate, molybdenum acrylate, molybdenum methacrylate, molybdenumvalerate, molybdenum gluconate, molybdenum citrate, molybdenum fumarate,molybdenum lactate, molybdenum maleate, molybdenum oxalate, molybdenum2-ethylhexanoate, molybdenum neodecanoate, molybdenum naphthenate,molybdenum stearate, molybdenum oleate, molybdenum benzoate, andmolybdenum picolinate.

Suitable molybdenum organophosphates include molybdenum dibutylphosphate, molybdenum dipentyl phosphate, molybdenum dihexyl phosphate,molybdenum dibeptyl phosphate, molybdenum dioctyl phosphate, molybdenumbis(1-methylheptyl)phosphate, molybdenum bis(2-ethylhexyl)phosphate,molybdenum didecyl phosphate, molybdenum didodecyl phosphate, molybdenumdioctadecyl phosphate, molybdenum dioleyl phosphate, molybdenum diphenylphosphate, molybdenum bis(p-nonylphenyl)phosphate, molybdenum butyl (2ethylhexyl)phosphate, molybdenum(1-methylheptyl)(2-ethylhexyl)phosphate,and molybdenum(2-ethylhexyl)(p-nonylphenyl)phosphate.

Suitable molybdenum organophosphonates include molybdenum butylphosphonate, molybdenum pentyl phosphonate, molybdenum hexylphosphonate, molybdenum heptyl phosphonate, molybdenum octylphosphonate, molybdenum(1-methylheptyl)phosphonate,molybdenum(2-ethylhexyl)phosphonate, molybdenum decyl phosphonate,molybdenum dodecyl phosphonate, molybdenum octadecyl phosphonate,molybdenum oleyl phosphonate, molybdenum phenyl phosphonate,molybdenum(p-nonylphenyl)phosphonate, molybdenum butyl butylphosphonate,molybdenum pentyl pentylphosphonate, molybdenum hexyl hexylphosphonate,molybdenum heptyl heptylphosphonate, molybdenum octyl octylphosphonate,molybdenum(1-methylheptyl)(1-methylheptyl)phosphonate,molybdenum(2-ethylhexyl)(2-ethylhexyl)phosphonate, molybdenum decyldecylphosphonate, molybdenum dodecyl dodecylphosphonate, molybdenumoctadecyl octadecylphosphonate, molybdenum oleyl oleylphosphonate,molybdenum phenyl phenylphosphonate,molybdenum(p-nonylphenyl)(p-nonylphenyl)phosphonate, molybdenumbutyl(2-ethylhexyl)phosphonate,molybdenum(2-ethylhexyl)butylphosphonate,molybdenum(1-methylheptyl)(2-ethylhexyl)phosphonate,molybdenum(2-ethylhexyl)(1-methylheptyl)phosphonate,molybdenum(2-ethylhexyl)(p-nonylphenyl)phosphonate, andmolybdenum(p-nonylphenyl)(2-ethylhexyl)phosphonate.

Suitable molybdenum organophosphinates include molybdenumbutylphosphinate, molybdenum pentylphosphinate, molybdenumhexylphosphinate, molybdenum heptylphosphinate, molybdenumoctylphosphinate, molybdenum(1-methylheptyl)phosphinate,molybdenum(2-ethylhexyl)phosphinate, molybdenum decylphosphinate,molybdenum dodecylphosphinate, molybdenum octadecylphosphinate,molybdenum oleylphosphinate, molybdenum phenylphosphinate,molybdenum(p-nonylphenyl)phosphinate, molybdenum dibutylphosphinate,molybdenum dipentylphosphinate, molybdenum dihexylphosphinate,molybdenum diheptylphosphinate, molybdenum dioctylphosphinate,molybdenum bis(1-methylheptyl)phosphinate, molybdenumbis(2-ethylhexyl)phosphinate, molybdenum didecylphosphinate, molybdenumdidodecylphosphinate, molybdenum dioctadecylphosphinate, molybdenumdioleylphosphinate, molybdenum diphenylphosphinate, molybdenumbis(p-nonylphenyl)phosphinate, molybdenumbutyl(2-ethylhexyl)phosphinate, molybdenum(1-methylheptyl)(2-ethylhexyl)phosphinate, andmolybdenum(2-ethylhexyl)(p-nonylphenyl)phosphinate.

Suitable molybdenum carbamates include molybdenum dimethylcarbamate,molybdenum diethylcarbamate, molybdenum diisopropylcarbamate, molybdenumdibutylcarbamate, and molybdenum dibenzylcarbamate.

Suitable molybdenum dithiocarbamates include molybdenumdimethyldithiocarbamate, molybdenum diethyldithiocarbamate, molybdenumdiisopropyldithiocarbamate, molybdenum dibutyldithiocarbamate, andmolybdenum dibenzyldithiocarbamate.

Suitable molybdenum xanthates include molybdenum methylxanthate,molybdenum ethylxanthate, molybdenum isopropylxanthate, molybdenumbutylxanthate, and molybdenum benzylxanthate.

Suitable molybdenum p-diketonates include molybdenum acetylacetonate,molybdenum trifluoroacetylacetonate, molybdenumhexafluoroacetylacetonate, molybdenum benzoylacetonate, molybdenum2,2,6,6-tetramethyl-3,5-heptanedionate, molybdenum dioxidebis(acetylacetonate), molybdenum dioxide bis(trifluoroacetylacetonate),molybdenum dioxide bis(hexafluoroacetylacetonate), molybdenum dioxidebis(benzoylacetonate), and molybdenum dioxidebis(2,2,6,6-tetramethyl-3,5-heptanedionate).

Suitable molybdenum alkoxides or aryloxides include molybdenummethoxide, molybdenum ethoxide, molybdenum isopropoxide, molybdenum2-ethylhexoxide, molybdenum phenoxide, molybdenum nonylphenoxide, andmolybdenum naphthoxide.

Suitable molybdenum halides include molybdenum hexafluoride, molybdenumpentafluoride, molybdenum tetrafluoride, molybdenum trifluoride,molybdenum pentachloride, molybdenum tetrachloride, molybdenumbichloride, molybdenum tetrabromide, molybdenum tribromide, molybdenumtriiodide, and molybdenum diiodide.

Suitable molybdenum pseudo-halides include molybdenum cyanide,molybdenum cyanate, molybdenum thiocyanate, and molybdenum azide.

Suitable molybdenum oxyhalides include molybdenum oxytetrafluoride,molybdenum dioxydifluoride, molybdenum oxytetrachloride, molybdenumoxytrichloride, molybdenum dioxydichloride, molybdenum oxytribromide,and molybdenum dioxydibromide.

The term “organomolybdenum compound” refers to any molybdenum compoundcontaining at least one molybdenum-carbon bond. Some specific examplesof suitable organomolybdenum compounds include tris(allyl)molybdenum,tris(methallyl)molybdenum, tris(crotyl)molybdenum,bis(cyclopentadienyl)molybdenum,bis(pentamethylcyclopentadienyl)molybdenum, bis(ethylbenzene)molybdenum,bis(mesitylene)molybdenum, bis(pentadienyl)molybdenum,bis(2,4-dimethylpentadienyl)molybdenum, bis(allyl)tricarbonylmolybdenum,(cyclopentadienyl)(pentadienyl)molybdenum, tetra(1-norbornyl)molybdenum(trimethylenemethane) tetracarbonylmolybdenum,bis(butadiene)dicarbonylmolybdenum, (butadiene)tetracarbonylmolybdenum,and bis(cyclooctatetraene)molybdenum.

Useful hydrogen phosphite compounds that can be employed as ingredient(b) of the molybdenum-based catalyst composition utilized in thisinvention are either acyclic hydrogen phosphites, cyclic hydrogenphosphites, or mixtures thereof. These compounds are described above.

The molybdenum-based catalyst composition further comprises anorganoaluminum compound, which has been designated as ingredient (c). Asused herein, the term “organoaluminum compound” refers to any aluminumcompound containing at least one aluminum-carbon bond. Organoaluminumcompounds that are soluble in a hydrocarbon solvent are preferablyemployed.

A preferred class of organoaluminum compounds is represented by thegeneral formula AIR_(n)X_(3-n), where each R, which may be the same ordifferent, is a mono-valent organic group that is attached to thealuminum atom via a carbon atom, where each X, which may be the same ordifferent, is a hydrogen atom, a halogen atom, a carboxylate group, analkoxide group, or an aryloxide group, and where n is an integer of 1 to3. Preferably, each R is a hydrocarbyl group such as, but not limitedto, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atom, or the appropriate minimum number of carbon atoms to formthe group, up to about 20 carbon atoms. These hydrocarbyl groups maycontain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. Preferably, each X is acarboxylate group, an alkoxide group, or an aryloxide group, with eachgroup preferably containing from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to about 20 carbonatoms.

Suitable types of organoaluminum compounds that can be utilized include,but are not limited to, trihydrocarbylaluminum, dihydrocarbylaluminumhydride, hydrocarbylaluminum dihydride, hydrocarbylaluminum dihalide,dihydrocarbylaluminum halide, dihydrocarbylaluminum carboxylate,hydrocarbylaluminum bis(carboxylate), dihydrocarbylaluminum alkoxide,hydrocarbylaluminum dialkoxide, dihydrocarbylaluminum aryloxide,hydrocarbylaluminum diaryloxide, and the like, and mixtures thereof.Trihydrocarbylaluminum compounds are generally preferred.

Suitable organoaluminum compounds include trimethylaluminum,triethylaluminum, triisobutylaluminum, tri-n-propylaluminum,triisopropylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum,tri-n-octylaluminum, tricyclohexylaluminum, triphenylaluminum,tri-p-tolylaluminum, tribenzylaluminum, diethylphenylaluminum,diethyl-p-tolylaluminum, diethylbenzylaluminum, ethyldiphenylaluminum,ethyldi-p-tolylaluminum, ethyldibenzylaluminum, diethylaluminum hydride,di-n-propylaluminum hydride, diisopropylaluminum hydride,di-n-butylaluminum hydride, diisobutylaluminum hydride,di-n-octylaluminum hydride, diphenylaluminum hydride, di-p-tolylaluminum hydride, dibenzylaluminum hydride, phenylethylaluminum hydride,phenyl-n-propylaluminum hydride, phenylisopropylaluminum hydride,phenyl-n-butylaluminum hydride, phenylisobutylaluminum hydride, phenyl-noctylaluminum hydride, p-tolylethylaluminum hydride,p-tolyl-n-propylaluminum hydride, p-tolylisopropylaluminum hydride,p-tolyl-n-butylaluminum hydride, p-5-tolyl-isobutylaluminum hydride,p-tolyl-n-octylaluminum hydride, benzylethylaluminum hydride,benzyl-n-propylaluminum hydride, benzylisopropylaluminum hydride,benzyl-n-butylaluminum hydride, benzylisobutylaluminum hydride, andbenzyl-n-octylaluminum hydride, ethylaluminum dihydride,n-propylaluminum dibydride, isopropylaluminum dihydride, n-butylaluminumdihydride, isobutylaluminum dihydride, n-octylaluminum dibydride,dimethylaluminum chloride, diethyl aluminum chloride, diisobutylaluminumchloride, dimethylaluminum bromide, diethylaluminum bromide,dimethylaluminum fluoride, diethylaluminum fluoride, methylaluminumdichloride, ethylaluminum dichloride, isobutyl aluminum dichloride,methylaluminum dibromide, ethylaluminum dibromide, methylaluminumdifluoride, ethylaluminum difluoride, methylaluminum sesquichloride,ethylaluminum sesquichloride, isobutylaluminum sesquichloride,dimethylaluminum hexanoate, diethylaluminum octoate, diisobutylaluminum2-ethylhexanoate, dimethylaluminum neodecanoate, diethylaluminumstearate, diisobutylaluminum oleate, methylaluminum bis(hexanoate),ethylaluminum bis(octoate), isobutylaluminum bis(2-ethylhexanoate),methyl-aluminum bis(neodecanoate), ethylaluminum bis(stearate),isobutylaluminum bis(oleate), dimethylaluminum methoxide,diethylaluminum methoxide, diisobutylaluminum methoxide,dimethylaluminum ethoxide, diethylaluminum ethoxide, diisobutylaluminumethoxide, dimethylaluminum phenoxide, diethylaluminum phenoxide,diisobutylaluminum phenoxide, methylaluminum dimethoxide, ethylaluminumdimethoxide, isobutylaluminum dimethoxide, methylaluminum diethoxide,ethylaluminum diethoxide, isobutylaluminum diethoxide, methylaluminumdiphenoxide, ethylaluminum diphenoxide, isobutylaluminum diphenoxide,and the like, and mixtures thereof.

Another class of organoaluminum compounds that can be utilized isaluminoxanes. Aluminoxanes are well known in the art and compriseoligomeric linear aluminoxanes that can be represented by the generalformula:

and oligomeric cyclic aluminoxanes that can be represented by thegeneral formula:

where x is an integer of 1 to about 100, preferably about 10 to about50; y is an integer of 2 to about 100, preferably about 3 to about 20;and each R₆, which may be the same or different, is a mono-valentorganic group that is attached to the aluminum atom via a carbon atom.Preferably, each R₆ is a hydrocarbyl group such as, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atoms, or the appropriate minimum number of carbon atoms toform the group, up to about 20 carbon atoms. These hydrocarbyl groupsmay contain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. It should be noted that thenumber of moles of the aluminoxane as used in this application refers tothe number of moles of the aluminum atoms rather than the number ofmoles of the oligomeric aluminoxane molecules. This convention iscommonly employed in the art of catalysis utilizing aluminoxanes.

In general, aluminoxanes can be prepared by reactingtrihydrocarbylaluminum compounds with water. This reaction can beperformed according to known methods, such as (1) a method in which thetrihydrocarbylaluminum compound is dissolved in an organic solvent andthen contacted with water, (2) a method in which thetrihydrocarbylaluminum compound is reacted with water of crystallizationcontained in, for example, metal salts, or water adsorbed in inorganicor organic compounds, and (3) a method in which thetrihydrocarbylaluminum compound is added to the monomer or monomersolution that is to be oligomerized, and then water is added.

Examples of aluminoxane compounds include methylaluminoxane (MAO),modified methylaluminoxane (MMAO), ethylaluminoxane, butylaluminoxane,isobutylaluminoxane, and the like, and mixtures thereof.Isobutylaluminoxane is particularly useful on the grounds of itsavailability and its solubility in aliphatic and cycloaliphatichydrocarbon solvents. Modified methylaluminoxane can be formed bysubstituting about 20-80% of the methyl groups of methylaluminoxane withC₂ to C₁₂ hydrocarbyl groups, preferably with isobutyl groups, by usingtechniques known to those skilled in the art.

Iron-based catalyst compositions are described in co-pending patentapplication U.S. Ser. No. 09/172,305, and U.S. Pat. Nos. 6,180,734 and6,211,313, which are incorporated herein by reference. The iron-basedcatalyst compositions are formed by combining (a) an iron-containingcompound, (b) a hydrogen phosphite, and (c) an organoaluminum compound.

Various iron-containing compounds or mixtures thereof can be employed asingredient (a) of the iron-based catalyst composition utilized in thisinvention. Iron-containing compounds that are soluble in a hydrocarbonsolvent such as aromatic hydrocarbons, aliphatic hydrocarbons, orcycloaliphatic hydrocarbons are preferably used. Hydrocarbon-insolubleiron-containing compounds, however, can be suspended in thepolymerization medium to form the catalytically active species, and aretherefore also useful.

The iron atom in the iron-containing compounds can be in variousoxidation states including, but not limited to, the 0, +2, +3, and +4oxidation states. Divalent iron compounds (also called ferrouscompounds), wherein the iron is in the +2 oxidation state, and trivalentiron compounds (also called ferric compounds), wherein the iron is inthe +3 oxidation state are preferred. Suitable types of iron-containingcompounds that can be utilized in this invention include, but are notlimited to, iron carboxylates, iron carbamates, iron dithiocarbamates,iron xanthates, iron β-diketonates, iron alkoxides, iron aryloxides, andorganoiron compounds.

Suitable iron carboxylates include iron (II) formate, iron(III) formate,iron(II) acetate, iron(III) acetate, iron(II) acrylate, iron(III)acrylate, iron(II) methacrylate, iron(III) methacrylate, iron(II)valerate, iron(III) valerate, iron(II) gluconate, iron(III) gluconate,iron(II) citrate, iron(III) citrate, iron(II) fumarate, iron(III)fumarate, iron(II) lactate, iron(III) lactate, iron(II) maleate,iron(III) maleate, iron(II) oxalate, iron(III) oxalate, iron(II)2-ethylhexanoate, iron(III) 2-ethylhexanoate, iron(II) neodecanoate,iron(III) neodecanoate, iron(II) naphthenate, iron(III) naphthenate,iron(II) stearate, iron(III) stearate, iron(II) oleate, iron(III)oleate, iron(II) benzoate, iron(III) benzoate, iron(II) picolinate, andiron (III) picolinate.

Suitable iron carbamates include iron (II) dimethylcarbamate, iron(III)dimethylcarbamate, iron(II) diethylcarbamate, iron(III)diethylcarbamate, iron(II) diisopropylcarbamate, iron(III)diisopropylcarbamate, iron(II) dibutylcarbamate, iron(III)dibutylcarbamate, iron(II) dibenzylcarbamate, and iron(III)dibenzylcarbamate.

Suitable iron dithiocarbamates include iron(II) dimethyldithiocarbamate,iron(III) dimethyldithiocarbamate, iron(II) diethyldithiocarbamate,iron(III) diethyldithiocarbamate, iron(II) diisopropyldithiocarbamate,iron(III) diisopropyldithiocarbamate, iron(II) dibutyldithiocarbamate,iron(III) dibutyldithiocarbamate, iron(II) dibenzyldithiocarbamate, andiron (III) dibenzyldithiocarbamate.

Suitable iron xanthates include iron (II) methylxanthate, iron(III)methylxanthate, iron(II) ethylxanthate, iron(III) ethylxanthate,iron(II) isopropylxanthate, iron(III) isopropylxanthate, iron(II)butylxanthate, iron(III) butylxanthate, iron(II) benzylxanthate, andiron(III) benzylxanthate.

Suitable iron β-diketonates include iron (II) acetylacetonate, iron(III) acetylacetonate, iron(II) trifluoroacetylacetonate, iron(III)trifluoroacetylacetonate, iron(II) hexafluoroacetylacetonate, iron(III)hexafluoroacetylacetonate, iron(II) benzoylacetonate, iron(III)benzoylacetonate, iron(II) 2,2,6,6-tetramethyl-3,5-heptanedionate, andiron(III) 2,2,6,6-tetramethyl-3,5-heptanedionate.

Suitable iron alkoxides or aryloxides include iron(II) methoxide,iron(III) methoxide, iron(II) ethoxide, iron(III) ethoxide, iron(II)isopropoxide, iron(III) isopropoxide, iron(II) 2-ethylhexoxide,iron(III) 2-ethylhexoxide, iron(II) phenoxide, iron(III) phenoxide,iron(II) nonylphenoxide, iron(III) nonylphenoxide, iron(II) naphthoxide,and iron(III) naphthoxide.

The term “organoiron compound” refers to any iron compound containing atleast one iron-carbon bond. Some specific examples of suitableorganoiron compounds include bis(cyclopentadienyl)iron(II) (also calledferrocene), bis(pentamethylcyclopentadienyl)iron(II) (also calleddecamethylferrocene), bis(pentadienyl) iron (II),bis(2,4-dimethylpentadienyl) iron (II), bis(allyl) dicarbonyliron (II),(cyclopentadienyl)(pentadienyl)iron(II), tetra(1-norbornyl)iron(IV),(trimethylenemethane)tricarbonyliron(II), bis(butadiene)carbonyliron(0),butadienetricarbonyliron(0), and bis(cyclooctatetraene)iron(0).

Useful hydrogen phosphite compounds that can be employed as ingredient(b) of the iron-based catalyst composition utilized in this inventionare either acyclic hydrogen phosphite, cyclic hydrogen phosphites, ormixtures thereof. These compounds are described above.

Useful organoaluminum compounds that can be employed as ingredient (c)of the molybdenum-based catalyst composition, described above, are alsosuitable for use as ingredient (c) of the iron-based catalystcomposition.

The catalyst compositions utilized in this invention have very highcatalytic activity for polymerizing 1,3-butadiene into syndiotactic1,2-polybutadiene over a wide range of total catalyst concentrations andcatalyst ingredient ratios. The polymers having the most desirableproperties, however, are obtained within a narrower range of totalcatalyst concentrations and catalyst ingredient ratios. Further, it isbelieved that the three catalyst ingredients (a), (b), and (c) caninteract to form an active catalyst species. Accordingly, the optimumconcentration for any one catalyst ingredient is dependent upon theconcentrations of the other catalyst ingredients.

With respect to the chromium-based catalyst composition, the molar ratioof the hydrogen phosphite to the chromium-containing compound (P/Cr) canbe varied from about 0.5:1 to about 50:1, more preferably from about 1:1to about 25:1, and even more preferably from about 2:1 to about 10:1.The molar ratio of the organomagnesium compound to thechromium-containing compound (Mg/Cr) can be varied from about 1:1 toabout 50:1, more preferably from about 2:1 to about 30:1, and even morepreferably from about 3:1 to about 20:1.

With respect to the molybdenum-based or iron-based catalystcompositions, the molar ratio of the hydrogen phosphite to themolybdenum containing compound (P/Mo) or to the iron-containing compound(P/Fe) can be varied from about 0.5:1 to about 50:1, more preferablyfrom about 1:1 to about 25:1, and even more preferably from about 2:1 toabout 10:1. Where ingredient (c) of the catalyst composition comprisesan organoaluminum compound defined by the formula AIR_(n)X_(3-n), themolar ratio of the organoaluminum compound to the molybdenum-containingcompound (Al/Mo) or to the iron-containing compound (Al/Fe) can bevaried from about 1:1 to about 100:1, more preferably from about 3:1 toabout 50:1, and even more preferably from about 5:1 to about 25:1. Wheningredient (c) of the catalyst composition utilized in the presentinvention comprises an aluminoxane, the molar ratio of the aluminoxaneto the molybdenum-containing compound (Al/Mo) or to the iron-containingcompound (Al/Fe) can be varied from about 5:1 to about 500:1, morepreferably from about 10:1 to about 200:1, and even more preferably fromabout 20:1 to about 100:1.

The catalyst composition is preferably formed by combining the threecatalyst ingredients (a), (b), and (c). Although an active catalystspecies is believed to result from this combination, the degree ofinteraction or reaction between the various ingredients or components isnot known with any great degree of certainty. Therefore, it should beunderstood that the term “catalyst composition” has been employed toencompass a simple mixture of the ingredients, a complex of the variousingredients that is caused by physical or chemical forces of attraction,a chemical reaction product of the ingredients, or a combination of theforegoing.

The catalyst composition utilized to prepare the syndiotactic1,2-polybutadiene can be formed by combining or mixing the catalystingredients or components by using, for example, one of the followingmethods:

First, the catalyst composition may be formed in situ by adding thethree catalyst ingredients to the rubber cement containing the rubberyelastomer and 1,3-butadiene monomer in either a stepwise or simultaneousmanner. When adding the catalyst ingredients in a stepwise manner, thesequence in which the ingredients are added is not critical. With regardto the chromium-based catalyst, the organomagnesium compound ispreferably added first, followed by the chromium-containing compound,and then followed by the hydrogen phosphite. With regard to themolybdenum-based or iron-based catalyst, the molybdenum-containing oriron-containing compound is preferably added first, followed by thehydrogen phosphite, and then followed by the organoaluminum compound.

Second, the three catalyst ingredients may be pre-mixed outside thepolymerization system at an appropriate temperature, which is generallyfrom about −20° C. to about 80° C., and the resulting catalystcomposition is then added to the rubber cement containing the rubberyelastomer and 1,3-butadiene monomer.

Third, the catalyst composition may be pre-formed in the presence ofconjugated diene monomer. That is, the three catalyst ingredients arepre-mixed in the presence of a small amount of conjugated diene monomerat an appropriate temperature, which is generally from about −20° C. toabout 80° C. The amount of 1,3-butadiene monomer that is used for thecatalyst pre-forming can range from about 1 to about 500 moles, morepreferably from about 4 to about 100 moles, and even more preferablyfrom about 10 to about 50 moles per mole of the chromium-containing,molybdenum-containing, or iron-containing compound. The resultingcatalyst composition is then added to the rubber cement containing therubbery elastomer and the 1,3-butadiene monomer that is to bepolymerized.

Fourth, as a further variation, the catalyst composition can also beformed by using a two-stage procedure. The first stage involvescombining the chromium-containing compound and the organomagnesiumcompound or the molybdenum-containing or iron-containing compound andthe organoaluminum compound, in the presence of a small amount ofconjugated diene monomer at an appropriate temperature, which isgenerally from about −20° C. to about 80° C. In the second stage, theforegoing reaction mixture and the hydrogen phosphite are charged ineither a stepwise or simultaneous manner to the rubber cement containingthe rubbery elastomer and the 1,3-butadiene monomer that is to bepolymerized.

Fifth, an alternative two-stage procedure may also be employed. Achromium-ligand, molybdenum-ligand, or iron-ligand, complex is firstformed by pre-combining the chromium-containing compound,molybdenum-containing compound, or iron-containing and the hydrogenphosphite compound. Once formed, the chromium complex is then combinedwith the organomagnesium compound, or the molybdenum or iron complex iscombined with the organoaluminum compound, respectively, to form theactive catalyst species. The complex can be formed separately or in therubber cement containing the rubbery elastomer and the 1,3-butadienemonomer that is to be polymerized. This complexation reaction can beconducted at any convenient temperature at normal pressure, but for anincreased rate of reaction, it is preferred to perform this reaction atroom temperature or above. The time required for the formation of thecomplex is usually within the range of about 10 minutes to about 2 hoursafter mixing the chromium-containing, molybdenum-containing oriron-containing compound with the hydrogen phosphite compound. Thetemperature and time used for the formation of the complex will dependupon several variables including the particular starting materials andthe solvent employed. Once formed, the complex can be used withoutisolation from the complexation reaction mixture. If desired, however,the complex may be isolated from the complexation reaction mixturebefore use.

Sixth, the three catalyst ingredients may be added to the rubber cementprior to or simultaneously with the addition of 1,3-butadiene monomer.

When a solution of the catalyst composition or one or more of thecatalyst ingredients is prepared outside the polymerization system asset forth in the foregoing methods, an organic solvent or carrier ispreferably employed. Useful organic solvents are described above.Organic solvents may serve to dissolve the catalyst composition oringredients, or the solvent may simply serve as a carrier in which thecatalyst composition or ingredients may be suspended.

The production of blends of syndiotactic 1,2-polybutadiene and rubberyelastomers according to this invention is accomplished by polymerizing1,3-butadiene monomer within the rubber cement by using a catalyticallyeffective amount of at least one of the foregoing catalyst compositions.The total catalyst concentration to be employed in the polymerizationmass depends on the interplay of various factors such as the purity ofthe ingredients, the polymerization temperature, the polymerization rateand conversion desired, and many other factors. Accordingly, a specifictotal catalyst concentration cannot be definitively set forth except tosay that catalytically effective amounts of the respective catalystingredients should be used. Generally, the amount of thechromium-containing, molybdenum-containing, or iron-containing compoundused can be varied from about 0.01 to about 2 mmol per 100 g of1,3-butadiene monomer, more preferably from about 0.02 to about 1.0 mmolper 100 g of 1,3-butadiene monomer, and even more preferably from about0.05 to about 0.5 mmol per 100 g of 1,3-butadiene monomer.

In performing the polymerization of 1,3-butadiene into syndiotactic1,2-polybutadiene within the rubber cement, a molecular weight regulatormay be employed to control the molecular weight of the syndiotactic1,2-polybutadiene to be produced. As a result, the scope of thepolymerization system can be expanded in such a manner that it can beused for the production of syndiotactic 1,2-polybutadiene having a widerange of molecular weights. Suitable types of molecular weightregulators that can be utilized include, but are not limited to,α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,1-heptene, and 1-octene; accumulated diolefins such as allene and1,2-butadiene; nonconjugated diolefins such as 1,6-octadiene,5-methyl-1,4-hexadiene, 1,5-cyclooctadiene, 3,7-dimethyl-1,6-octadiene,1,4-cyclohexadiene, 4-vinylcyclohexene, 1,4-pentadiene, 1,4-hexadiene,1,5-hexadiene, 1,6-heptadiene, 1,2-divinylcyclohexane,5-ethylidene-2-norbornene, 5-methylene-2-norbornene,5-vinyl-2-norbornene, dicyclopentadiene, and 1,2,4-trivinylcyclohexane;acetylenes such as acetylene, methylacetylene and vinylacetylene; andmixtures thereof. The amount of the molecular weight regulator used,expressed in parts per hundred parts by weight of the 1,3-butadienemonomer (phm), is from about 0.01 to about 10 phm, more preferably fromabout 0.02 to about 2 phm, and even more preferably from about 0.05 toabout 1 phm.

The molecular weight of the syndiotactic 1,2-polybutadiene to beproduced can also be effectively controlled by conducting thepolymerization of 1,3-butadiene monomer in the presence of hydrogen gas.In this case, the partial pressure of hydrogen gas is preferably fromabout 0.01 to about 50 atmospheres.

The polymerization of 1,3-butadiene into syndiotactic 1,2-polybutadienewithin the rubber cement may be carried out as a batch process, acontinuous process, or even a semi-continuous process. In thesemi-continuous process, 1,3-butadiene monomer is intermittently chargedas needed to replace that monomer already polymerized. In any case, thepolymerization is desirably conducted under anaerobic conditions byusing an inert protective gas such as nitrogen, argon or helium, withmoderate to vigorous agitation. The polymerization temperature may varywidely from a low temperature, such as −10° C. or below, to a hightemperature such as 100° C. or above, with a preferred temperature rangebeing from about 20° C. to about 90° C. The heat of polymerization maybe removed by external cooling, cooling by evaporation of the1,3-butadiene monomer or the solvent, or a combination of the twomethods. Although the polymerization pressure employed may vary widely,a preferred pressure range is from about 1 atmosphere to about 10atmospheres.

Once a desired conversion is achieved, the polymerization of1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within therubber cement can be stopped by adding a polymerization terminator thatinactivates the catalyst system. Typically, the terminator employed toinactivate the catalyst system is a protic compound, which includes, butis not limited to, an alcohol, a carboxylic acid, an inorganic acid,water, or a combination thereof. An antioxidant such as2,6-di-tert-butyl-4-methylphenol may be added along with, before orafter the addition of the terminator. The amount of the antioxidantemployed is usually in the range of 0.2% to 1% by weight of the polymerproduct. When the polymerization reaction has been stopped, the blend ofsyndiotactic 1,2-polybutadiene and the rubbery elastomer can berecovered from the polymerization mixture by utilizing conventionalprocedures of desolventization and drying. For instance, the blend ofsyndiotactic 1,2-polybutadiene and the rubbery elastomer may be isolatedfrom the polymerization mixture by coagulation of the polymerizationmixture with an alcohol such as methanol, ethanol, or isopropanol, or bysteam distillation of the solvent and the unreacted 1,3-butadienemonomer, followed by filtration. The product is then dried to removeresidual amounts of solvent and water. The polymer blend produced is ahighly dispersed blend of crystalline syndiotactic 1,2-polybutadiene inthe rubbery elastomer.

Advantageously, the catalyst composition employed in this invention canbe manipulated to vary the characteristics of the syndiotactic1,2-polybutadiene in the polymer blend. Namely, the syndiotactic1,2-polybutadiene in the polymer blend made by the process of thisinvention can have various melting temperatures, molecular weights,1,2-linkage contents, and syndiotacticities, all of which are dependentupon the selection of the catalyst ingredients and the ingredientratios.

The blends of syndiotactic 1,2-polybutadiene and rubbery elastomersproduced with the process of this invention have many uses. For example,these blends can be utilized in rubber compositions that are used tomanufacture the supporting carcass, innerliner, sidewall, and tread oftires. The blends of syndiotactic 1,2-polybutadiene and rubberyelastomers are also useful in the manufacture of films and packagingmaterials and in many molding applications.

In a preferred embodiment, the blend of syndiotactic 1,2-polybutadienein rubbery elastomer is added to rubber compositions that are useful inthe manufacture of tires. As is generally known in the art, these rubbercompositions or tire formulations include a base rubber, filler,vulcanizing agent, and sundry additional additives that are common inrubber compounding.

Both synthetic and natural rubber may be employed within the rubbercompositions. These rubbers, which may also be referred to aselastomers, include, without limitation, natural rubber, syntheticpolyisoprene, poly(styrene-co-butadiene), polybutadiene,poly(styrene-co-butadiene-co-isoprene), poly(styrene-co-isoprene), andmixtures thereof.

The rubber compositions may include fillers such as inorganic andorganic fillers. Organic fillers include carbon black. Inorganic fillersinclude silica, aluminum hydroxide, magnesium hydroxide, and clays(hydrated aluminum silicates).

A multitude of rubber vulcanizing agents, which are also referred to ascuring agents, can be employed within these rubber compositions. Forexample, sulfur or peroxide-based curing systems may be employed. Also,see Kirk Othmer, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, 3^(rd) Edition,Wiley Interscience,

30N.Y. 1982, Vol. 20, pp. 365-468, particularly VULCANIZATION AGENTS ANDAUXILIARY MATERIALS pp. 390-402, or Vulcanization by A. Y. Coran,ENCYCLOPEDIA OF POLYMER SCIENCE AND ENGINEERING, 2^(nd) Edition, JohnWiley & Sons, Inc., 1989, which are incorporated herein by reference.Vulcanizing agents may be used alone or in combination.

The rubber compositions may also include other compounding additivessuch as accelerators, oils, waxes, scorch inhibiting agents, processingaids, antidegradants, zinc oxide, optional tackifying resins, optionalreinforcing resins, optional fatty acids, and optional peptizers.

In one preferred embodiment, a blend of syndiotactic 1,2-polybutadieneand EPDM, prepared according to the process of this invention, isemployed with a rubber composition that is useful for the manufacture oftire sidewalls. The preferred blend includes from about 0.4 to about 12parts by weight SPB and from about 99.6 to about 88 parts by weightEPDM. More preferably, the blend includes from about 2 to about 10 partsby weight SPB and from about 98 to about 90 parts by weight EPDM.

When practicing this embodiment, the blend is combined and compoundedwith a base rubber in an amount from about 1 to about 40 parts by weightblend phr, preferably from about 2 to about 20 parts by weight phr, andeven more preferably from about 5 to about 10 parts by weight blend phr.

Sidewall formulations also typically include a filler, which is employedin an amount from about 10 to about 70 parts by weight phr, preferablyfrom 20 about 20 to about 60 parts by weight phr, and more preferablyfrom about 25 to about 50 parts by weight phr.

The syndiotactic 1,2-polybutadiene within the EPDM rubbery elastomerthat is utilized in tire sidewall formulations preferably has a meltingtemperature from about 70 to about 210° C., more preferably from about90 to about 195° C., and even more preferably from about 110° C. toabout 190° C.

Fillers are typically employed in an amount from about 1 to about 100parts by weight phr, and preferably from about 20 to about 90 parts byweight phr, and more preferably from about 40 to about 80 parts byweight pier.

Those skilled in the art will be able to choose a useful amount of theother ingredients that may be employed in these rubber compositions. Forexample, it is generally known in the art of making tire components thatsulfur is typically employed in an amount from about 0.5 to about 10parts by weight phr, and preferably from about 1 to about 6 parts byweight phr. Oils are typically employed in an amount from about 1 toabout 60 parts by weight phr, and preferably in an amount from about 1to about 50 parts by weight phr. Zinc oxide is typically employed in anamount from about 0.5 to about 8 by weight phr, and preferably fromabout 1 to about 5 parts by weight phr.

Rubber formulations are compounded by using mixing equipment andprocedures conventionally employed in the art. Preferably, an initialmasterbatch is prepared that includes the rubber component and thereinforcing fillers, as well as other optional additives such asprocessing oil and antidegradants. The blend of syndiotactic1,2-polybutadiene and EPDM is preferably added during preparation of theinitial masterbatch. This masterbatch is typically mixed at temperaturesin excess of about 100 or 150° C. To prevent premature vulcanization,also known as scorch, the initial masterbatch generally excludes thevulcanizing agent. Once the initial masterbatch is prepared, thevulcanizing agent is blended into the composition at lower temperatures.Rubber compounding techniques and the additives employed therein aregenerally known as disclosed in The Compounding and Vulcanization ofRubber, by Stevens in RUBBER TECHNOLOGY SECOND EDITION (1973 VanNostrand Reihold Company). The mixing conditions and proceduresapplicable to silica-filled tire formulations are also well known asdescribed in U.S. Pat. Nos. 5,227,425; 5,719,207; 5,717,022, as well asEP 0890606, all of which are incorporated herein by reference.

The rubber compositions can then be processed into tire components,including sidewalls, according to ordinary tire manufacturing techniquesincluding standard rubber molding and curing techniques. Typically,vulcanization is effected by heating the vulcanizable composition in amold; e.g., it is heated to about 170° C. Cured or crosslinked rubbercompositions may be referred to as vulcanizates, which generally containthree-dimensional polymeric networks that are thermoset. The otheringredients, such as fillers, oils, and antidegradants, are generallydispersed throughout the network.

While the blends of this invention are preferably added to formulationsused to make tire sidewalls, the blend can also be used within othertire components such as treads, subtreads, body ply skims, bead fillersand the like. Pneumatic tires can be made as discussed in U.S. Pat. Nos.5,866,171; 5,876,527; 5,931,211; and 5,971,046, which are incorporatedherein by reference.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested as described in theExamples disclosed hereinbelow. The examples should not, however, beconstrued as limiting the scope of the invention. The claims will serveto define the invention.

EXAMPLES Example 1 Preparation of sPB/EPDM Blend

A highly dispersed blend of syndiotactic 1,2-polybutadiene and EPDM wasprepared by polymerizing 1,3-butadiene monomer into syndiotactic1,2-polybutadiene within an EPDM rubber cement.

The EPDM rubber cement was prepared by dissolving 50 g of EPDM to form asolution containing 15% by weight solids by dissolving in 300 grams ofhexane. The EPDM contained about 56% ethylene, about 6%5-ethylidene-2-norborene, had a number average molecular weight (M_(n))of 60,000 and a Mooney Viscosity (ML₁₊₄@100° C.) of about 35.

At room temperature, adding 12 grams of a 1,3-butadiene/hexane blendcontaining 22.4% by weight of 1,3-butadiene were added to the EPDMrubber cement produced above. The polymerization of the 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene was initiated by theaddition of 6.25 mL of 0.032 M iron (III) 2-ethylhexanoate in hexanes,0.27 mL of 2.93 M bis(2-ethylhexyl)hydrogen phosphite in hexanes, and6.0 mL of 0.68 M triisobutylaluminum in hexanes. The polymerization wasconducted at 50° C. for 6 hours. The polymerization was stopped by theaddition of 3 mL of isopropanol diluted with 50 mL of hexanes. Thepolymerization mixture was added into 10 liters of isopropanolcontaining 12 g of 2,6-di-tert-butyl-4-methylphenol. The polymer blendof 3% syndiotactic 1,2-polybutadiene in EPDM was isolated by filtrationand dried to a constant weight under vacuum of 60° C. Differentialscanning calorimetry (DSC) revealed a broad Tm peak, between 190°-205°C., that was attributed to the formation of syndiotactic1,2-polybutadiene. A blend containing 6% syndiotactic 1,2-polybutadienein EPDM and a blend containing 12% syndiotactic 1,2-polybutadiene inEPDM were prepared exactly as above, except that the amounts of1,3-butadiene monomer and catalyst components were adjusted.

Analysis showed that SPB did form within the EPDM as evidenced bymelting temperature peaks (Tm) within a DSC curve.

Example 2 Preparation of a 6% sPB/EPDM blend

Approximately 50 grams of an EPDM sample (E/P=55/45, M_(n)=60 k, thediene is 5-ethylidene-2-norbornene or ENB, 6%) was dissolved in 450 mLof hexanes to form a solution containing 15% solids. A mixture of1,3-butadiene (Bd) monomer in hexanes was charged (5.0 grams total ofBd) followed by the addition of Fe(EHA)₃ (0.1 mmol) in hexanes,HPO(OEH)₂ (0.4 mmol) in hexanes and TIBA (2 mmol) in hexanes. Themixture was agitated at 50° C. for 6 hours. The reaction mixture waspoured into isopropyl alcohol with agitation, isolated, air-dried, andthen vacuum-dried to remove any remaining solvent. The polymer mixturewas analyzed by differential scanning calorimetry (DSC) which revealed abroad T_(m) peak (T_(m)=190-205° C.) attributed to the formation of thesPB.

Examples 3-4 Application of the sPB-EPDM In-Situ Blend in Black SidewallEPDM Formulation

TABLE 1 Formulations for Examples 3-4 Example 3 4 Formulation PHR PHRJSR EP35* 40 Example 1 blend 40 cis-Polybutadiene 40 40 Natural Rubber20 20 Carbon Black 50 50 Aromatic Oil 17 17 Stearic Acid 2 2 Sulfur 1.51.5 Zinc Oxide 3 3 Accelerators Total 0.5 0.5 *Note: JSR EP35 is an EPDMavailable from Japan synthetic rubber.

TABLE 2 Mixing conditions for Examples 3-4 using a brabender mixer.Master Batch Remill Final Start Temp. ° C. 100 100 70 Dump Temp. ° C.160 160 100 Time (min.) 5 5 2 RPM 60 60 40

TABLE 3 Properties of Examples 3-4 Stock 3 4 ML 1 + 4 130° C. 35.1 38.2Ring Tensile at 23° C. 622 664 EB % TB 9.27 8.44 M100 1.29 1.11Dynastst, Tan Delta at 50° C. 0.194 0.189 Ring Tear at 23° C., EB % 578673 Tear Strength (normalized) 1 1.07

ML 1+4 130° C. was measured using ASTM-D1646. Ring Tensile at 23° C., EB% was measured using ASTM-D412. Tan Delta at 50° C. was measured using aDynastat Viscosity Analyzer. Ring Tear at 23° C., EB % was measuredusing ASTM-624.

TABLE 4 Cut Growth Rate of Examples 3-4 Stock 3 4 Crack GrowthResistance 51 45 Dc/Dn (nm/cycle) at 50° C. Tearing Energy (J/m²) 12101145

Dc/Dn (nm/cycle) was measured in a “pure shear” geometry with a precut[Reference: Lake G J, Rubber Chemistry and Technology, 68: (3), 435-460,1995]. The testing sheet had a length of 20.32 cm, a height of 64.5 mmand a thickness of 2 mm. A pre-cut of 4.0 cm was made along the lengthdirection. Cyclic deformation was applied along the height directionwith a strain amplitude of 2.5% to 25%, and with a frequency of 1 to 100Hz. The testing condition was a 40 Hz half-sinusoidal pulse for a 5 HZdeformation cycle under 10% strain amplitude at various temperatures(23° C.-80° C.). Images of the propagating crack were recordedautomatically at a given interval of about 10,000 cycles. Crack growthrate (dc/dn) is then calculated by the increment of crack length at eachcycle (nm/cycles). This type of cut growth rate of 45 and below isadvantageous in many applications.

Although the present invention has been described in the above exampleswith reference to particular means, materials and embodiments, it wouldbe obvious to persons skilled in the art that various changes andmodifications may be made, which fall within the scope claimed for theinvention as set out in the appended claims. The invention is thereforenot limited to the particulars disclosed and extends to all equivalentswithin the scope of the claims.

1-18. (canceled)
 19. A method for making a polymeric compositioncomprising: mixing a rubber cement and 1,3-butadiene monomer, whereinthe rubber cement comprises an elastomeric terpolymer polymerized fromethylene, at least one α.-olefin monomer, and at least one dienemonomer; polymerizing the 1,3-butadiene monomer into syndiotactic1,2-polybutadiene within the rubber cement by using a catalystcomposition that is formed by combining (a) a chromium-containingcompound, (b) a hydrogen phosphite, and (c) an organomagnesium compoundor (a) a molbydenum-containing compound or an iron-containing compound,(b) a hydrogen phosphite, and (c) an organoaluminum compound; formingthe composition into a tire sidewall.
 20. The method of claim 19,wherein the catalyst composition is added to the mixture of rubbercement and 1,3-butadiene monomer such that the chromium-containingcompound, the molybdenum-containing compound, or the iron-containingcompound is present in an amount of about 0.01 to about 2 mmol per 100 gof 1,3-butadiene.
 21. The method of claim 19, wherein the syndiotactic1,2-polybutadiene has a melting temperature of from about 70° C. toabout 210° C.
 22. The method of claim 19, wherein the mixture ofsyndiotactic 1,2-polybutadiene and elastomeric terpolymer comprises fromabout 3 percent to about 12 percent by weight of syndiotactic1,2-polybutadiene.
 23. The method of claim 19, wherein a test sheet ofthe composition has a cut growth rate of 45 Dc/Dn (nm/cycle) and belowat 50° C.
 24. The method of claim 19, wherein the α-olefin monomer ispropylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene,or a combination thereof.
 25. The method of claim 19, wherein the dienemonomer is 5-ethylidene-2-norbornene, 1,4-hexadiene,5-methylene-2-norbornene, 1,6-octadiene, 5-methyl-1,4-hexadiene,3,7-methyl-1,6-octadiene, 1,3-cyclopentadiene, 1,4-cyclohexadiene,dicyclopentadiene, 5-vinyl-2-norbornene, or a combination thereof. 26.The method of claim 19, wherein said catalyst composition is added tothe mixture of rubber cement and 1,3-butadiene monomer such that thechromium-containing compound, the molybdenum-containing compound, or theiron-containing compound is present in an amount of about 0.01 to about2 mmol per 100 g of 1,3-butadiene.
 27. The method of claim 19, whereinthe elastomeric terpolymer is ethylene-propylene-diene terpolymer.
 28. Atire sidewall comprising: a polymeric component including an elastomericterpolymer polymerized from ethylene, at least one α.-olefin monomer,and at least one diene monomer; and syndiotactic 1,2-polybutadiene. 29.The tire sidewall of claim 28, wherein the α-olefin monomer ispropylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene,or a combination thereof.
 32. The tire sidewall of claim 28, wherein thesyndiotactic 1,2-polybutadiene has a melting temperature of from about70° C. to about 210° C.
 30. The tire sidewall of claim 28, wherein thediene monomer is 5-ethylidene-2-norbornene, 1,4-hexadiene,5-methylene-2-norbornene, 1,6-octadiene, 5-methyl-1,4-hexadiene,3,7-methyl-1,6-octadiene, 1,3-cyclopentadiene, 1,4-cyclohexadiene,dicyclopentadiene, 5-vinyl-2-norbornene, or a combination thereof. 31.The tire sidewall of claim 28, wherein the polymeric component comprisesfrom about 3 percent to about 12 percent by weight of syndiotactic1,2-polybutadiene.
 32. The tire sidewall of claim 28, wherein a testsheet of the tire sidewall has a cut growth rate of 45 Dc/Dn (nm/cycle)and below at 50° C.
 33. The tire sidewall of claim 28, wherein theelastomeric terpolymer is ethylene-propylene-diene terpolymer.
 34. Thetire sidewall of claim 28, wherein the composition includes a chromium-,iron-, or molybdenum-containing compound, (b) a hydrogen phosphite, and(c) an organomagnesium or organoaluminum compound.
 35. The tire sidewallof claim 28, wherein the syndiotactic 1,2-polybutadiene is catalyzedwith a combination of (a) a chromium-containing compound, (b) a hydrogenphosphite, and (c) an organomagnesium compound or (a) amolbydenum-containing compound or an iron-containing compound, (b) ahydrogen phosphite, and (c) an organoaluminum compound
 36. The tiresidewall claim 28, further comprising cis-polybutadiene.
 37. The tiresidewall of claim 28, further comprising natural rubber.
 38. The methodof claim 19, further comprising mixing in an additional elastomerselected from the group consisting of: cis-polybutadiene, naturalrubber, and mixtures thereof.